Packet communication system, packet communication method, base station, mobile station, controller and packet communication program

ABSTRACT

A system is provided in which capacity and satisfaction rate with a quality of service in packet communications performed through a radio link established between a transmitting station and a receiving station is improved by dynamically limiting transmission power of packets in the transmitting station and keeping an increase of an interference level in the receiving station, which belongs to another cell, within a TPC margin. The present invention includes a resource allocator configured to set transmission power of packets in a next step period, by use of transmission power of packets in a preceding step period (slot) and an interference level of the receiving station.

TECHNICAL FIELD

The present invention relates to a packet communications system, apacket communications method, a base station, a mobile station, acontrol device and a packet communications program, all of which are forperforming packet communications through a radio link establishedbetween a transmitting station and a receiving station.

BACKGROUND ART

In a conventional packet communications system, upon receipt of a packetaddressed to a mobile station, a base station allocates radio resources(power resources and the like) up to maximum available transmissionpower of the base station, and transmits the packet to the mobilestation. For example, in a CDMA system, upon receipt of a packetaddressed to a mobile station, a base station allocates code resourcesup to maximum available transmission power of the base station, andtransmits the packet to the mobile station.

In the conventional packet communications system as described above,when packets arrive at a base station in a burst way, transmission powerof packets in the base station significantly fluctuates temporally.Thus, fluctuation of an interference level (interference power) in amobile station belonging to another cell becomes large.

FIG. 1 shows a schematic configuration of a conventional packetcommunications system in a downlink. In this drawing, it is assumed thata base station BS1 controls a cell (area) “A” and communicates withmobile stations MS1 and MS3 which are located in this cell “A”, and abase station BS2 controls a cell “B” and communicates with a mobilestation MS2 which is located in this cell “B”. Description will be givenbelow while focusing on reception situations in the mobile station MS2.

In a packet communications system performing transmission power control(TPC), based on an interference level received by a receiving station inan immediately preceding slot, transmission power of packets of atransmitting station in a next slot is determined so as to have a targetSIR (signal-to-interference power ratio) which is obtained by adding aTPC margin to a required SIR of the receiving station.

For example, in the packet communications system performing thetransmission power control, as shown in FIG. 2C, based on aninterference level received by the mobile station MS2 in a slot 1 (seeFIG. 2B), transmission power of a packet addressed to the mobile stationMS2 in the base station BS2 is determined so as to have a target SIR(for example, 4 dB) which is obtained by adding a TPC margin (forexample, 1 dB) to a required SIR (for example, 3 dB).

However, as shown in FIG. 2A, when a large quantity of packets arrive atthe base station BS1 in a slot 2, the base station BS1 allocates coderesources up to maximum available transmission power of the base stationBS1. Thus, compared to total transmission power of the base station BS1in the slot 1, total transmission power of the base station BS1 in theslot 2 is drastically increased. As a result, as shown in FIG. 2B, theinterference level in the mobile station MS2 from the base station BS1is rapidly increased in the slot 2. Therefore, as shown in FIG, 20, inthe mobile station MS2, an SIR of a received signal falls below therequired SIR to cause packet reception failure.

As described above, the conventional packet communications systemdescribed above has a drawback in that, regardless of the TPC margin,the rapid increase of the interference level in the receiving stationdue to burstiness of packets causes the packet reception failure in manycases. Moreover, there is a drawback in that such packet receptionfailure deteriorates a communications quality and decreases a systemcapacity.

DISCLOSURE OF THE INVENTION

The present invention was made in consideration of the abovecircumstances, It is an object of the present invention to provide apacket communications system, a packet communications method, a basestation, a mobile station, a control device and a packet communicationsprogram, which are capable of improving satisfaction rate with a systemcapacity and a quality of service (QoS) by dynamically limitingtransmission power of packets in a transmitting station and keeping anincrease of an interference level in a receiving station belonging toanother cell within a TPC margin.

In order to achieve the foregoing object, a first aspect of the presentinvention is summarized as a packet communications system which performspacket communications through a radio link established between atransmitting station and a receiving station. The packet communicationssystem includes a transmission power setter configured to settransmission power of packets in a next step period, by use oftransmission power of packets in a preceding step period and aninterference level of the receiving station.

Moreover, the first aspect of the present invention is summarized as apacket communications system which performs packet communicationsthrough a radio link established between a base station and a mobilestation. The packet communications system includes: step setting meansfor changing transmission power for each of step periods of apredetermined length when one or a plurality of packets are transmittedin the radio link; and transmission power limiting means for settingtransmission power in a next step period by use of transmission power ina preceding step period and an interference level for the mobilestation.

A second aspect of the present invention is summarized as a packetcommunications method for performing packet communications through aradio link established between a transmitting station and a receivingstation. The packet communications method includes setting transmissionpower of packets in a next step period by use of transmission power ofpackets in a preceding step period and an interference level of thereceiving station.

Moreover, the second aspect of the present invention is summarized as apacket communications method for performing packet communicationsthrough a radio link established between a base station and a mobilestation. The packet communications method includes: a step (1) ofchanging transmission power for each of step periods of a predeterminedlength when one or a plurality of packets are transmitted in the radiolink; and a step (2) of setting transmission power in a next step periodby use of transmission power in a preceding step period and aninterference level for the mobile station.

A third aspect of the present invention is summarized as a base stationwhich performs packet communications through a radio link establishedbetween the base station and a mobile station. The base station includesa transmission power setter configured to set transmission power ofpackets in a next step period by use of transmission power of packets ina preceding step period and an interference level of the mobile station.

Moreover, the third aspect of the present invention is summarized as abase station which performs packet communications through a radio linkestablished between the base station and a mobile station. The basestation includes; step setting means for changing transmission power foreach of step periods of a predetermined length when one or a pluralityof packets are transmitted in the radio link; and transmission powerlimiting means for setting transmission power in a next step period byuse of transmission power in a preceding step period and an interferencelevel for the mobile station.

A fourth aspect of the present invention is summarized as a mobilestation which performs packet communications through a radio linkestablished between the mobile station and a base station. The mobilestation includes: an interference level average value obtainerconfigured to obtain an average value of interference levels received bythe base station in a preceding fixed period through an announcementsignal from the base station; and a transmission power setter configuredto set transmission power of packets in a next step period by use oftransmission power of packets in a preceding step period and the averageof interference levels.

Moreover, the fourth aspect of the present invention is summarized as amobile station which performs packet communications through a radio linkestablished between the mobile station and a base station. The mobilestation includes: interference level obtaining means for obtaining anaverage level of interference received by the base station in animmediately preceding fixed period of time in order to changetransmission power at the base station side for each of step periods ofa predetermined length when one or a plurality of packets aretransmitted in the radio link, the average level being obtained throughan announcement signal from the base station; and transmission powerlimiting means for setting transmission power in a next step period byuse of transmission power in a preceding step period and the obtainedinterference level.

A fifth aspect of the present invention is summarized as a controldevice which controls packet communications performed through a radiolink established between a transmitting station and a receiving station.The control device includes a transmission power setter configured toset transmission power of packets in a next step period by use oftransmission power of packets in a preceding step period and aninterference level of the receiving station.

Moreover, the fifth aspect of the present invention is summarized as acontrol device which controls each base station which performs packetcommunications through a radio link established between the base stationand a mobile station. The control device includes: step setting meansfor changing transmission power for each of step periods of apredetermined length when one or a plurality of packets are transmittedin the radio link; and transmission power limiting means for settingtransmission power in a next step period by use of transmission power ina preceding step period and an interference level for the mobilestation.

In the fifth aspect of the present invention, it is preferable that atransmission power storage configured to store the transmission power ofpackets in the preceding step period, and a transmission power limitvalue calculator configured to calculate a transmission power limitvalue in the next step period by use of the transmission power ofpackets stored in the transmission power storage are further included,and the transmission power setter is configured to set the transmissionpower of packets in the next step period to be smaller than or equal tothe transmission power limit value.

Moreover, in the fifth aspect of the present invention, it is preferablethat a quality of service monitor configured to monitor a quality ofservice in the radio link is further included, and the transmissionpower setter is configured to set the transmission power of packets inthe next step period to exceed the transmission power limit value withinmaximum available transmission power of the transmitting station whenthe quality of service is smaller than or equal to a predeterminedvalue.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power setter is configured to set the transmissionpower of the packets in the next step period in accordance with aninterference level of the transmitting station when the transmissionpower of packets in the preceding step period is 0.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power setter is configured to set the transmissionpower of packets in the next step period based on an average value ofinterference levels received by the transmitting station in a precedingfixed period.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power setter is configured to set the transmissionpower of packets in the next step period in accordance with an averagevalue of transmission power of packets in a preceding fixed period whenthe transmission power of packets in the preceding step period is 0.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power limiting means includes: transmission powerstorage means for storing transmission power in each of the stepperiods; and limit value calculation means for calculating atransmission power limit value in the next step period by use of thetransmission power stored in the transmission power storage means, andthe transmission power limiting means sets transmission power in thenext step period to be smaller than or equal to the transmission powerlimit value.

Moreover, in the fifth aspect of the present invention, it is preferablethat request quality monitoring means for monitoring QoS for the radiolink is further included, and the transmission power limiting means hasa function of setting the transmission power of packets to exceed atransmission power limit in the step period within maximum transmissionpower when the QoS is smaller than or equal to a predetermined value.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power limiting means sets transmission power inthe next step period in accordance with an interference level at thebase station side when transmission power in the step period is 0.

Moreover, in the fifth aspect of the present invention, it is preferablethat interference level announcement means for informing the mobilestation of an average level of interference received by the base stationin an immediately preceding fixed period of time by use of anannouncement signal to the mobile station from the base station isfurther included, and the transmission power limiting means has afunction of setting the transmission power based on announcement fromthe interference level announcement means.

Moreover, in the fifth aspect of the present invention, it is preferablethat the transmission power limiting means sets transmission power inthe next step period in accordance with average transmission power ofthe base station before a fixed period of time when transmission powerin the step period is 0.

A sixth aspect of the present invention is summarized as a packetcommunications program which performs packet communications through aradio link established between a transmitting station and a receivingstation. The program allows a computer to execute processing of settingtransmission power of packets in a next step period by use oftransmission power of packets in a preceding step period and aninterference level of the receiving station.

Moreover, the sixth aspect of the present invention is summarized as apacket communications program which performs packet communicationsthrough a radio link established between a base station and a mobilestation. The packet communications program allows a computer to executeprocessing which includes: a step (1) of changing transmission power foreach of step periods of a predetermined length when one or a pluralityof packets are transmitted in the radio link; and a step (2) of settingtransmission power in a next step period by use of transmission power ina preceding step period and an interference level for the mobilestation.

A seventh aspect of the present invention is summarized as a controldevice which controls packet communications performed through a radiolink established between a transmitting station and a receiving station.The control device includes a resource allocator configured to allocatea radio resource in a next step period by use of total reception powerof packets from the transmitting station in a preceding step period andthe quantity of packets accumulated in the transmitting station.

An eighth aspect of the present invention is summarized as a basestation which performs packet communications through a radio linkestablished between the base station and a mobile station. The basestation includes a resource allocator configured to allocate a radioresource in a next step period by use of total reception power ofpackets from the mobile station in a preceding step period and thequantity of packets accumulated in the mobile station.

A ninth aspect of the present invention is summarized as a packetcommunications program which performs packet communications through aradio link established between a transmitting station and a receivingstation. The program allows a computer to execute processing ofallocating a radio resource in a next step period by use of totalreception power of packets from the transmitting station in a precedingstep period and the quantity of packets accumulated in the transmittingstation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an overview of a conventionalpacket communications system.

FIG. 2A is a graph showing total transmission power of a base stationBS1 for each period of time (slot) in a downlink in the conventionalpacket communications system.

FIG. 2B is a graph showing an interference level of a mobile station MS2for each period of time (slot) in the downlink in the conventionalpacket communications system.

FIG. 2C is a graph showing transmission power of a packet addressed tothe mobile station MS2 in a base station BS2 for each period of time(slot) in the downlink in the conventional packet communications system.

FIG. 2D is a graph showing an SIR of a received signal in the mobilestation MS2 for each period of time (slot) in the downlink in theconventional packet communications system.

FIG. 3 is an explanatory diagram showing an overview of a packetcommunications system according to a first embodiment of the presentinvention.

FIG. 4 is an explanatory diagram showing an overview of a base stationaccording to the first embodiment of the present invention.

FIG. 5A is a graph showing total transmission power of a base stationBS1 for each period of time (slot) in a downlink in the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 5B is a graph showing an interference level of a mobile station MS2for each period of time (slot) in the downlink in the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 5C is a graph showing transmission power of a packet addressed tothe mobile station MS2 in a base station BS2 for each period of time(slot) in the downlink in the packet communications system according tothe first embodiment of the present invention.

FIG. 5D is a graph showing an SIR of a received signal in the mobilestation MS2 for each period of time (slot) in the downlink in the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 6A is a view showing a state of transmitting packets whileexceeding a transmission power limit value in the packet communicationssystem according to the first embodiment of the present invention.

FIG. 6B is a graph showing total transmission power of a base stationBS1 for each period of time (slot) in a downlink in the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 7 is a block diagram showing an internal configuration of the basestation according to the first 6 embodiment of the present invention.

FIG. 8 is a flowchart showing operations of the packet communicationssystem according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an overview of a packetcommunications system according to a second embodiment of the presentinvention.

FIG. 10 is an explanatory diagram showing an overview of a mobilestation according to the second embodiment of the present invention.

FIG. 11A is a graph showing total transmission power of a mobile stationMS3 for each period of time (slot) in an uplink in the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 11B is a graph showing an interference level of a base station BS3for each period of time (slot) in the uplink in the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 11C is a graph showing transmission power of a packet addressed tothe base station BS1 in a mobile station MS1 for each period of time(slot) in the uplink in the packet communications system according tothe second embodiment of the present invention.

FIG. 11D is a graph showing an SIR of a received signal in the mobilestation MS1 for each period of time (slot) in the uplink in the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 11E is a graph showing an interference level of a base station BS2for each period of time (slot) in the uplink in the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 11F is a graph showing transmission power of a packet addressed tothe base station BS1 in a mobile station MS2 for each period of time(slot) in the uplink in the packet communications system according tothe second embodiment of the present invention.

FIG. 11G is a graph showing an SIR of a received signal in the mobilestation MS2 for each period of time (slot) in the uplink in the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 12 is a block diagram showing an internal configuration of themobile station according to the second embodiment of the presentinvention.

FIG. 13 is a cubic diagram showing a computer-readable recording mediumrecording a packet communications program according to a thirdembodiment of the present invention.

FIG. 14 is a table used for determining a transmission power limit valuein a next step period in the packet communications system according tothe first embodiment of the present invention.

FIG. 15 is a table used for determining a transmission power limit valuein a next step period in the packet communications system according tothe second embodiment of the present invention.

FIG. 16 is a flowchart showing operations of the packet communicationssystem according to the second embodiment of the present invention.

FIG. 17 is a block diagram showing an internal configuration of a basestation according to the third embodiment of the present invention.

FIG. 18 is a block diagram showing an internal configuration of a mobilestation according to the third embodiment of the present invention.

FIG. 19 is a sequence diagram showing operations of a packetcommunications system according to the third embodiment of the presentinvention.

BEST MODES FOR CARRYING OUT THE INVENTION First Embodiment Overview ofPacket Communications System and Packet Communications Method Accordingto this Embodiment

Detailed description will be given below of a packet communicationssystem and a packet communications method according to a firstembodiment of the present invention. FIG. 3 is an explanatory viewshowing an overview of the packet communications system according tothis embodiment.

Note that, in the packet communications system according to thisembodiment, a base station (transmitting station) BS2 controlstransmission power of packets addressed to a mobile station (receivingstation) MS2 in a downlink (a direction toward the mobile station MS2from the base station BS2).

As shown in FIG. 3, in the packet communications system according tothis embodiment, a base station BS1 controlling a cell “A” and the basestation BS2 controlling a cell “B” adjacent to the cell “A” aredisposed. Mobile stations MS1 and MS3 are located in the cell “A” andthe mobile station MS2 is located in the cell “B”. FIG. 4 shows aschematic configuration of the base stations BS1 and BS2 according tothis embodiment.

In the case where a large quantity of packets arrive at the base stationBS1, the base station BS1 determines a transmission power limit value ina next slot when transmitting packets from a transmission buffer via thedownlink (downward channel). Specifically, the base station BS1determines the transmission power limit value in accordance withtransmission power and a TPC margin in a preceding slot (a step periodof a predetermined length) so as not to significantly increase aninterference level in the mobile station MS2 belonging to the other cell“B”.

To be more specific, as shown in FIG. 5A, the base station BS1 increases(changes) the transmission power limit value in stages for each periodof time (slots 1 to 3) within maximum available transmission power ofthe base station BS1.

Consequently, as shown in FIG. 5B, the interference level in the mobilestation MS2 which is located in the cell “B” from the base station BS1is also increased in stages. Here, as shown in FIG. SC, in accordancewith the interference level of the mobile station MS2 in the slot 1, thebase station BS2 determines transmission power of packets addressed tothe mobile station MS2 in the slot 2 so as to have a target SIR which isobtained by adding a TPC margin to a required SIR.

Thus, an increase of the interference level in the mobile station MS2can be suppressed to the TPC margin or less. In addition, as shown inFIG. 5D, a SIR of a received signal in the mobile station MS2 can beincreased to be larger than the required SIR, and reception failure canbe prevented.

Hereinafter, description will be given of a method for calculating atransmission power limit value for keeping the increase of theinterference level in the mobile station MS2 within the TPC margin.

Note that, here, a required SIN R in the mobile station M$2 and a TPCmargin are expressed as “SIN R_(th)” and “TPC_(margin)”, respectively,(both of which are true values, in other words, both of which do nottake on values of “dB”) and a noise level (noise power) in the mobilestation MS2 is expressed as “N”. Here, when transmission power ofpackets (total transmission power) of the base station BS1 in the slot 1is “P₁”, an increase of transmission power of packets of the basestation BS1 in the slot 2 (that is, a step width) _(n)P₁ is calculated,

First, an interference level caused to the mobile station MS2 by thetotal transmission power of the base station BS1 is considered. Here, itis assumed that an interference level caused to the mobile station MS2by the total transmission power PI of the base station BS1 in the slot 1is “I”, and an increase of the interference level in the mobile stationMS2 is “_(n)I” when the transmission power of the base station BS1 isincreased by “_(n)P₁” in the slot 2.

Based on the required SIN R of the mobile station MS2, the TPC marginand the noise level in the slot 1, the base station BS1 using thetransmission power control calculates desired wave signal power S in theslot 2, as shown in the following expression. Specifically, the desiredwave signal power S is calculated as below.S=(SINR _(th) ×TPC _(m) _(arg) _(in))(N+I)

Moreover, based on the calculated desired wave signal power S and theinterference level in the slot 2, the base station BS1 calculates an SINR in the slot 2, as shown in the following expression.

$\frac{S}{N + I + {\Delta\; I}} = \frac{\left( {{SIN}\; R_{th} \times {TPC}_{margin}} \right)\left( {N + I} \right)}{N + I + {\Delta\; I}}$

Accordingly, as a result of this calculation, if the SIN R is equal toSIN R_(th) or more, the mobile station MS2 succeeds in packet receptionin the slot 2. Specifically, in order for the mobile station MS2 tosucceed in the packet reception in the slot 2, it is required to satisfythe following condition.

$\frac{\left( {{SIN}\; R_{th} \times {TPC}_{margin}} \right)\left( {N + I} \right)}{N + I + {\Delta\; I}} \geq {{SIN}\; R_{th}}$As a result, the following expression is established.

$\frac{\Delta\; I}{I} \leq {\frac{\left( {{SIN}\; R_{th} \times {TPC}_{margin}} \right)\left( {1 + \frac{N}{I}} \right)}{{SIN}\; R_{th}} - 1 - \frac{N}{I}}$

Here, the noise level N is extremely small as compared to theinterference level I. Thus, in the above expression, the term “N/I” canbe regarded as “0”. Moreover, since “_(n)I/I” in the mobile station MS2is equal to “_(n)P₁/P₁” in the base station BS1, the above expressioncan be transformed as below,

$\frac{\Delta\; P_{1}}{P_{1}} \leq {\frac{\left( {{SIN}\; R_{th} \times {TPC}_{margin}} \right)}{{SIN}\; R_{th}} - 1}$

The above expression can be further transformed as below.

$\frac{\Delta\; P_{1}}{P_{1}} \leq {{TPC}_{margin} - 1}$

From the above expression, for the total transmission power P₁ of thebase station BS1 in the slot 1, a maximum value _(n)P₁ of the totaltransmission power of the base station BS1, which can be increased inthe slot 2, can be calculated.

Moreover, a transmission power limit value of the base station BS1 inthe slot 2 can be calculated from the following expression.ΔP ₁ +P ₁=(TPC _(m) _(arg) ^(in)−1)×P ₁ +P ₁ =TPC _(m) _(arg) ^(in) ×P ₁

For example, when the required SIN R (SINR_(th))=2 (3 dB) andTPC_(margin)=1.26 (1 dB), _(n)P₁=0.26 P₁. Specifically, the transmissionpower limit value of the base station BS1 in the slot 2 is 1.26 P₁.

By use of _(n)P₁ which is calculated as described above, in the slot 2,the base station BS1 allocates and transmits transmission power ofpackets by using “_(n)P₁+_(n)P₁” as the transmission power limit value.

As to the next slot and subsequent slots, the base station BS1calculates a transmission power limit value “P₁+_(n)P₁” in a slot (i+1)from transmission power of packets in a slot i. The maximum value of thetotal transmission power of the base station BS1, which can beincreased, is set to “_(n)P₁” as described above. Thus, it is possibleto avoid a rapid increase of the interference level in the mobilestation MS2 belonging to the other cell “B”.

Note that, when total transmission power in an immediately precedingslot is small, a maximum value of the total transmission power, whichcan be increased in a next slot, is limited. Thus, a packet transmissiondelay occurs.

In order to avoid such an adverse effect, in this embodiment, the basestation BS1 can transmit packets regardless of the transmission powerlimit value, for example, by referring to a packet delay and quality ofservice (QoS) such as buffering time.

For example, as shown in FIG. 6A, a bound “P₁+_(n)P₁” is provided as thetransmission power limit value of the base station BS1 in the slot 2.Then, when there is a packet exceeding a predetermined delay threshold,as shown in FIG. 6B, the base station BS1 can repeat packet transmissionprocessing (ignore the bound of the transmission power limit value inthe slot 2) before transmitting the packet exceeding the delaythreshold, within the maximum available transmission power of the basestation BS1.

Moreover, when transmission power of packets in a preceding slot is “0”,the base station BS1 determines a transmission power limit value in anext slot as below. Here, when the transmission power of packets in thepreceding slot is smaller than a predetermined threshold, the basestation BS1 may determine the transmission power of packets to be “0”.

To be more specific, when traffic is empty, the interference level inthe mobile station MS2 belonging to the cell “B”, which is differentfrom the cell “A” controlled by the base station BS1, is low. Thus, evenif the increase _(n)P₁ of the transmission power of packets in the basestation BS1 is small, the interference level exceeding the TPC margin ismore likely to be caused in the mobile station MS2.

On the contrary, when the traffic is busy, the interference level in themobile station MS2 belonging to the cell “B” is high. Thus, even if theincrease _(n)P₁ of the transmission power of packets in the base stationBS1 is large, the required SIR is satisfied in the mobile station MS2and reception of packets from the base station BS2 is more likely to besuccessful.

Therefore, it is required to determine the increase _(n)P₁ of thetransmission power of packets in the next step period in accordance withthe interference level in the mobile station MS2, that is, how busy thetraffic is.

In this embodiment, when transmission power of packets in a precedingstep period is “0”, the base station BS1 can determine the transmissionpower of packets in a next step period in accordance with a proportionoccupied by an average value of transmission power of packets in acertain period in the maximum available transmission power P_(max) ofthe base station BS1.

For example, as shown in FIG. 14, when the proportion of the averagevalue of the transmission power of packets (average transmission power)in a certain period of time (for example, n frames) in the maximumavailable transmission power (traffic load) is “0 to ⅓”, “⅓ to ⅔” or “⅔to 1”, a transmission power limit value P0_max in the next step periodis set to “ 1/10”, “ 2/10” or “ 3/10” of the maximum availabletransmission power of the base station BS1, respectively.

Configuration of Base Station According to this Embodiment

In order to realize the packet communications system according to thisembodiment, the base stations BS1 and BS2 have a configuration as below.Since the base stations BS1 and BS2 include basically the samefunctions, the base station BS2 will be described below. FIG. 7 is ablock diagram showing the configuration of the base station BS1according to this embodiment.

As shown in FIG. 7, as uplink (upward direction) processing means., thebase station BS2 includes an upward interference level storage circuit101, a demodulation circuit 102, a decoding circuit 103 and a signalseparation circuit 116.

The upward interference level storage circuit 101 is a storage deviceconfigured to detect and store interference levels in the uplink to thebase station BS2 from the mobile stations MS1 to MS3. The interferencelevels stored in this upward interference level storage circuit 101 areoutputted to a downward announcement circuit 109.

The demodulation circuit 102 is an arithmetic circuit configured todemodulate an upward signal obtained via the uplink, and the decodingcircuit 103 is an arithmetic circuit configured to produce upwardinformation by decoding the demodulated upward signal.

The signal separation circuit 116 is configured to separate aninterference level in the mobile station MS2 from the upwardinformation, and to output the interference level to a transmissionpower limit value calculation circuit 113.

Moreover, as downlink (downward direction) processing means, the basestation BS2 includes a transmission buffer 117, the downwardannouncement circuit 109, a signal multiplexing circuit 108, a codingcircuit 110, a modulation circuit 111, a transmission power calculationstorage circuit 112, the transmission power limit value calculationcircuit 113, a QoS monitoring circuit 114 and a-resource allocationcircuit 115.

Here, in the base station BS2, the signal multiplexing circuit 108, thecoding circuit 110 and the modulation circuit 111 are included in apacket transmission circuit 214.

An upward interference level from the upward interference power levelstorage circuit 101 is inputted to the signal multiplexing circuit 108via the downward announcement circuit 109, and multiplexed with downwardinformation. Thereafter, the upward interference level is transmitted tothe mobile station MS2 as a downward signal via the coding circuit 110,the modulation circuit 111 and a circulator 115.

The transmission buffer 117 is configured to accumulate downwardinformation (for example, packets) addressed to a mobile station (forexample, MS2) which is located in the cell “B” controlled by the basestation BS2.

The downward announcement circuit 109 is a circuit configured to informpredetermined mobile stations MS1 to MS3 of an interference level in thebase station BS2, which is obtained from the upward interference levelstorage circuit 101. The downward announcement circuit 109 multiplexesan identification signal indicating the interference level into anannouncement signal in the signal multiplexing circuit 108,

The signal multiplexing circuit 108 is a circuit configured to multiplexmany pieces of downward information accumulated in the transmissionbuffer 117 and the announcement signal generated by the downwardannouncement circuit 109 for each of predetermined time slots.

The coding circuit 110 is a circuit configured to code a signalmultiplexed by the signal multiplexing circuit 108.

The modulation circuit 111 is a circuit configured to modulate thesignal coded by the coding circuit 110, by use of a radio resource (forexample, transmission power of packets, a code resource and the like)which is allocated by the resource allocation circuit 115.

The transmission power calculation storage circuit 112 is a circuitconfigured to store transmission power of packets in each of stepperiods (for example, slots) of a predetermined length. Specifically,the transmission power calculation storage circuit 112 is configured tostore transmission power of packets in a preceding step period, which isallocated by the resource allocation circuit 115.

The transmission power limit value calculation circuit 113 is a circuitconfigured to play a role of limit value calculation means forcalculating a transmission power limit value in the next step period, byuse of the transmission power stored in the transmission powercalculation storage circuit 112 (the transmission power in the precedingstep period).

Moreover, when the transmission power of packets in the preceding stepperiod is “0”, the transmission power limit value calculation circuit113 refers to the transmission power calculation storage circuit 112,and calculates the transmission power limit value in the next stepperiod based on an average value of transmission power of packets in apreceding fixed period.

Meanwhile, when the transmission power in the preceding step period is“0”, or more, the transmission power limit value calculation circuit 113calculates the transmission power limit value in the next step period inaccordance with the transmission power in the preceding step period.

The QoS monitoring circuit 114 is a quality of service monitorconfigured to monitor quality of service (QoS) in a radio link, forexample, packet delays of packets staying in the transmission buffer117, buffering time and the like.

The resource allocation circuit 115 is a circuit configured to allocatea radio resource for packet transmission in accordance with respectiveprocessing results of the circuits 112 to 114. For example, whentransmitting one or a plurality of packets in a predetermined radiolink, the resource allocation circuit 115 is configured to changetransmission power of each of the packets to be allocated for each ofthe step periods.

Specifically, the resource allocation circuit 115 constitutes atransmission power setter configured to set transmission power ofpackets in the next step period, by use of the transmission power ofpackets in the preceding step period, which is stored in thetransmission power calculation storage circuit 112, and the interferencelevel in the mobile station MS2, which is obtained from the signalseparation circuit 116.

Moreover, the resource allocation circuit 115 sets the transmissionpower of packets in the next step period to be smaller than or equal tothe transmission power limit value calculated by the transmission powerlimit value calculation circuit 113, and allocates a radio resourceaccording to the set transmission power of packets.

Moreover, when the QoS in the radio link is smaller than or equal to apredetermined value, the resource allocation circuit 115 sets thetransmission power of packets in the next step period to exceed thetransmission power limit value calculated by the transmission powerlimit value calculation circuit 113 within the maximum availabletransmission power of the base station BS2.

For example, when the QoS monitoring circuit 114 determines that thereis a packet exceeding the delay threshold, the resource allocationcircuit 115 allocates the radio resource to the packet even iftransmission power of the packet exceeds the transmission power limitvalue in the next step period.

Moreover, the resource allocation circuit 115 may set the transmissionpower of packets in the next step period based on an average value ofinterference levels received by the base station BS2 in a precedingfixed period.

The circulator 100 is a switching circuit configured to sort signalstransmitted/received between the base station BS2 and the mobile stationMS2. The circulator 100 outputs an upward signal received from themobile station MS2 to the uplink processing circuit, and transmits adownward signal processed by the downlink processing circuit to themobile station MS2.

Packet Communications Method According to this Embodiment

FIG. 8 shows a flowchart of a packet communications method according tothis embodiment.

As shown in FIG. 8, in Step S101, the base station BS2 determineswhether or not there is a packet addressed to the mobile station MS2 inthe transmission buffer 117.

When the base station BS2 determines that there is no packet addressedto the mobile station MS2 in the transmission buffer 117, the basestation BS2 becomes a stand-by state until a packet addressed to themobile station MS2 is accumulated in the transmission buffer 117 by loopprocessing.

Meanwhile, when the base station BS2 determines that there is a packetaddressed to the mobile station MS2 in the transmission buffer 117, thebase station BS2 determines, in Step S102, whether or not transmissionpower of packets (total transmission power) in a preceding slot (stepperiod) is “0”.

When the transmission power in the preceding slot is “0”, in Step S103,the transmission power limit value calculation circuit 113 of the basestation BS2 calculates a transmission power limit value in the next slotby referring to FIG, 14, that is, in accordance with the traffic load(the proportion of the average transmission power in the maximumavailable transmission power).

Meanwhile, when the transmission power in the preceding slot isdetermined not to be “0”, in Step S104, the transmission power limitvalue calculation circuit 113 of the base station BS2 decides thetransmission power limit value in the next slot in accordance with thetransmission power in the preceding slot.

In Step S105, the resource allocation circuit 115 of the base stationBS2 allocates radio resources within the transmission power limit valuecalculated by the transmission power limit value calculation circuit113, and the packet transmission circuit 118 transmits the packet to themobile station MS2 by use of the allocated radio resources.

In Step S106, the QoS monitoring circuit 114 determines whether or notthere is a packet exceeding a delay threshold in the packets staying inthe transmission buffer 117.

When there is the packet exceeding the delay threshold in thetransmission buffer 117, in Step S107, the resource allocation circuit115 allocates the radio resources to these packets until the maximumavailable transmission power of the base station BS2 is reached,regardless of the transmission power limit value calculated by thetransmission power limit value calculation circuit 113.

Meanwhile, when the packet exceeding the delay threshold are determinednot to exist in the transmission buffer, the packet communicationsmethod according to this embodiment returns to Step S101 and repeats theabove-described Steps S101 to S106.

Second Embodiment Overview of Packet Communications System and PacketCommunications Method According to this Embodiment

Next, detailed description will be given of a packet communicationssystem and a packet communications method according to a secondembodiment of the present invention. FIG. 9 is an explanatory viewshowing an overview of the packet communications system according tothis embodiment.

Note that, in the packet communications system according to thisembodiment, a mobile station (transmitting station) MS3 is configured tocontrol transmission power of a packet addressed to a base station(receiving station) BS1 in an uplink (a direction toward the basestation BS1 from the mobile station MS3).

As shown in FIG. 9, in the packet communications system according tothis embodiment, the base station BS1 controlling a cell “A” and a basestation BS2 controlling a cell “B” adjacent to the cell “A” aredisposed. Mobile stations MS1 and MS3 are located in the cell “A”, and amobile station MS2 is located in the cell “B”. FIG. 10 shows a schematicconfiguration of the mobile stations MS1 to MS3 according to thisembodiment.

As shown in FIGS. 11A to 11G, the packet communications system accordingto this embodiment can prevent packet reception failure in the mobilestations MS1 and MS2, by limiting total transmission power (transmissionpower of packets) of the mobile station MS3 in stages.

To be more specific, in accordance with transmission power of packets ina preceding slot (for example, a slot 1), the mobile station MS3 decidesa transmission power limit value in a next slot (for example, a slot 2).

In this embodiment, a method for deciding the transmission power limitvalue in the next slot is the same as that of the first embodimentexcept for the processing in the case where the transmission power ofpackets in the preceding slot is “0”.

Specifically, in the case of this embodiment, the base stations BS1 andBS2 inform the mobile stations MS2 and MS3 of interference levels in therespective base stations BS1 and BS2, by use of downward announcementsignals (for example, pilot signals, transmission permission probabilityannouncement signals and the like), Thereafter, the mobile station MS3decides the transmission power limit value in the next slot inaccordance with the informed interference levels.

Here, the base stations BS1 and BS2 inform the mobile stations MS2 andMS3, by use of announcement signals, of “identification signalsindicating the interference levels (for example, 1 to 3)”, whichcorrespond to “a proportion of the interference levels received by thebase stations BS1 and BS2 in a preceding fixed period in a maximuminterference level”, as “an average value of the interference levelsreceived by the base stations BS1 and BS2 in the preceding fixedperiod”.

Configuration of Mobile Station According to this Embodiment

In order to realize the packet communications system described above, inthis embodiment, the mobile stations MS1 to MS3 have a configuration asbelow. Since the mobile stations MS1 and MS3 include basically the samefunctions, the mobile station MS3 will be described below. FIG. 12 is ablock diagram showing the configuration of the mobile station MS3according to this embodiment.

As shown in FIG. 12, as downlink (downward direction) processing means,the mobile station MS3 includes a downward interference level storagecircuit 210, a demodulation circuit 201, a decoding circuit 202 and asignal separation circuit 203.

The downward interference level storage circuit 210 is a storage deviceconfigured to detect and store interference levels in the downlink tothe mobile station MS3 from the base stations BS1 and BS2. Theinterference levels stored in this downward interference level storagecircuit 210 are outputted to an upward announcement circuit 211.

The downward interference level from the downward interference powerlevel storage circuit 210 is inputted to a signal multiplexing circuit212 via the upward announcement circuit 211, and multiplexed with upwardinformation. Thereafter, the downward interference level is transmittedto the base station BS1 as an upward signal via a coding circuit 204, amodulation circuit 205 and a circulator 200.

The demodulation circuit 201 is an arithmetic circuit configured todemodulate downward signals obtained via the downlink from the basestation BS1. Moreover, the decoding circuit 202 is an arithmetic circuitconfigured to decode the demodulated downward signals.

The signal separation circuit 203 is a circuit configured to separatesignals required for calculating a transmission power limit value (forexample, announcement signals from the base station BS1) among thesignals decoded by the decoding circuit 202, and outputs the signals toa transmission power limit value calculation circuit 207 to be describedlater.

Moreover, as uplink (upward direction) processing means, the mobilestation MS3 includes a transmission buffer 213, the upward announcementcircuit 211, the signal multiplexing circuit 212, the coding circuit204, the modulation circuit 205, a transmission power calculationstorage circuit 206, the transmission power limit value calculationcircuit 207, a QoS monitoring circuit 208 and a resource allocationcircuit 209.

The transmission buffer 213 is configured to accumulate upwardinformation addressed to the base station BS1 (for example, packets)

The upward announcement circuit 211 is a circuit configured to informthe predetermined base stations BS1 and BS2 of an interference level inthe mobile station MS3, which is obtained from the downward interferencelevel storage circuit 210. The upward announcement circuit 211multiplexes the interference level in the mobile station MS3 into anannouncement signal in the signal multiplexing circuit 212.

The signal multiplexing circuit 212 is a circuit configured to multiplexmany pieces of upward information accumulated in the transmission buffer213 and the announcement signal generated by the upward announcementcircuit 212 for each of predetermined time plots.

The coding circuit 204 is a circuit configured to code the upwardinformation. Moreover, the modulation circuit 205 is a circuitconfigured to modulate the upward information coded by the codingcircuit 204, by use of radio resources (power resources and the like)which are allocated by the resource allocation circuit 209.

The transmission power calculation storage circuit 206 is a circuitconfigured to store transmission power of packets in each of stepperiods (for example, slots) of a predetermined length.

The transmission power limit value calculation circuit 207 is a circuitconfigured to play a role of limit value calculation means forcalculating a transmission power limit value in a next step period inaccordance with transmission power of packets in a preceding stepperiod, which is stored in the transmission power calculation storagecircuit 206, and information included in the announcement signalseparated in the signal separation circuit 203 (for example, an averagevalue of interference levels received by the base station BS1 in apreceding fixed period).

Moreover, when the transmission power of packets in the preceding stepperiod is “0”, the transmission power limit value calculation circuit207 calculates the transmission power limit value in the next stepperiod, by referring to FIG. 15 and using the information included inthe announcement signal separated in the signal separation circuit 203(for example, the average value of the interference levels received bythe base station BS1 in the preceding fixed period).

The QoS monitoring circuit 208 is a quality of service monitorconfigured to monitor quality of service (QoS) in a radio link.

The resource allocation circuit 209 is a circuit configured to allocateradio resources for packet transmission in accordance with respectiveprocessing results of the circuits 206 to 208. Specifically, whentransmitting one or a plurality of packets in a predetermined radiolink, the resource allocation circuit 209 changes transmission power ofeach of the packets to be allocated for each of the step periods.

Moreover, the resource allocation circuit 209 plays a role oftransmission power limiting means for limiting the transmission power ofpackets in the next step period to be smaller than or equal to thetransmission power limit value.

Moreover, when the QoS is smaller than or equal to a predeterminedvalue, in the next step period, the resource allocation circuit 209 mayset the transmission power of packets to exceed the transmission powerlimit within the maximum transmission power.

The circulator 200 is a switching circuit configured to sort signalstransmitted/received between the mobile station MS3 and the base stationBS1. The circulator 200 outputs an downward signal received from thebase station BS1 to the downlink processing circuit, and transmits anupward signal processed by the uplink processing circuit to the basestation

Packet Communications Method According to this Embodiment

FIG. 16 shows a flowchart of the packet communications method accordingto this embodiment. The packet communications method according to thisembodiment is the same as the packet communications method according tothe first embodiment except for an operation of Step S203 and a pointthat transmission power of packets is controlled by the mobile stationMS3. Hereinafter, these differences will be mainly described.

As shown in FIG. 16, in Step S201, the mobile station MS3 determineswhether or not there is a packet addressed to the base station MS1 inthe transmission buffer 213.

When the mobile station MS3 determines that there is no packet addressedto the base station BS1 in the transmission buffer 213, the mobilestation MS3 becomes a stand-by state until a packet addressed to thebase station BS1 is accumulated in the transmission buffer 213 by loopprocessing.

Meanwhile, when the mobile station MS3 determines that there is a packetaddressed to the base station BS1 in the transmission buffer 213, themobile station MS3 determines, in Step S202, whether or not transmissionpower of packets (total transmission power) in a preceding slot (stepperiod) is “0”.

When the transmission power in the preceding slot is determined not tobe “0”, in Step S204, the transmission power limit value calculationcircuit 207 of the mobile station MS3 decides the transmission powerlimit value in the next slot in accordance with the transmission powerin the preceding slot, which is stored in the transmission powercalculation storage circuit 206.

Meanwhile, when the transmission power in the preceding slot is “0”, inStep S203, the transmission power limit value calculation circuit 113 ofthe base station BS2 obtains an announcement signal, which istransmitted by the base station BS1, from the signal separation circuit203. Thereafter, the transmission power limit value calculation circuit113 refers to FIG. 15 and extracts a “transmission power limit value”corresponding to an “identification signal of an interference level”which is included in the announcement signal.

In Step S205, the resource allocation circuit 209 of the mobile stationMS3 allocates radio resources within the transmission power limit valuecalculated by the transmission power limit value calculation circuit207, and a packet transmission circuit 214 transmits the packet to thebase station BS1 by using the allocated radio resources such as powerresources.

In Step S206, the QoS monitoring circuit 208 determines whether or notthere is a packet exceeding a delay threshold in the packets staying inthe transmission buffer 213.

When there is the packet exceeding the delay threshold in thetransmission buffer 213, in Step S207, the resource allocation circuit209 allocates the radio resources to these packets until the maximumavailable transmission power of the mobile station MS3 is reached,regardless of the transmission power limit value calculated by thetransmission power limit value calculation circuit 207.

Meanwhile, when the packet exceeding the delay threshold are determinednot to exist in the transmission buffer 213, the packet communicationsmethod according to this embodiment returns to Step S201 and repeats theabove-described Steps S201 to S206.

Third Embodiment

Next, with reference to FIGS. 17 to 19, a packet communications systemand a packet communications method according to a third embodiment ofthe present invention will be described. FIG. 17 is a functional blockdiagram of a base station BS1 according to this embodiment and FIG. 18is a functional block diagram of a mobile station MS3 according to thisembodiment.

Hereinafter, description will be given of differences between the packetcommunications system and the packet communications method according tothis embodiment and the packet communications systems and the packetcommunications methods according to the first and second embodimentsdescribed above.

As shown in FIG. 17, the base station BS according to this embodimentincludes a reception power storage circuit 119 in addition to thefunctions of the base station BS according to the first embodiment shownin FIG. 7.

The reception power storage circuit 119 is a circuit configured to storea sum of reception power of packets transmitted from all mobile stationsMS in the base station in a preceding step period. Moreover, in responseto a request from the resource allocation circuit 115, the receptionpower storage circuit 119 provides the stored sum of the reception powerof packets.

Moreover, the signal separation circuit 116 extracts the quantity ofpackets accumulated in the transmission buffer 213 of the mobile stationMS from among upward information decoded by the decoding circuit 103,and transmits the quantity of packets to the resource allocation circuit115.

Moreover, based on a sum of reception power in a preceding step period,which is received from the reception power storage circuit 119, and thequantity of packets accumulated in the transmission buffer 213 of themobile station MS, which is received from the signal separation circuit116, the resource allocation circuit 115 allocates radio resources (coderesources, slot resources and the like) of the mobile station MS in anext step.

For example, based on the above-described sum of reception power in thepreceding step period, the resource allocation circuit 115 calculatestotal available reception power in the next step period.

Here, in the base station BS, transmission power control is performed atconstant reception power. Thus, reception power per code is the same.Therefore, based on the above-described total available reception powerin the next step period, the resource allocation circuit 115 cancalculate the number of codes which can be allocated in the next stepperiod.

Then, based on the above-described quantity of packets, the resourceallocation circuit 115 calculates the number of codes to be allocated tothe respective mobile stations MS from the number of codes which can beallocated.

The resource allocation circuit 115 transmits the number of codesallocated to the respective mobile stations MS to the modulation circuit111.

As shown in FIG. 18, the mobile station MS according to this embodimentincludes a packet quantity notification circuit 215 in addition to thefunctions of the mobile station MS according to the second embodimentshown in FIG. 12.

The packet quantity notification circuit 215 is a circuit configured tonotify the base station BS of the quantity of packets accumulated in thetransmission buffer 213 (such as an amount of data or the number ofpackets), by multiplexing the quantity of packets with controlinformation or upward packets in the signal multiplexing circuit 212.

Moreover, the packet quantity notification circuit 215 may periodicallynotify the base station BS of the quantity of packets accumulated in thetransmission buffer 213 without multiplexing the quantity of packetswith the control information or the upward packets.

The signal separation circuit 203 extracts radio resources (coderesources, slot resources and the like) in the next step period fromamong downward information decoded by the decoding circuit 202, andtransmits the radio resources to the resource allocation circuit 209.

In the next step period, the resource allocation circuit 209 allocatesradio resources for packet transmission in accordance with the radioresources transmitted from the signal separation circuit 203.

With reference to FIG. 19, the packet communications method according tothis embodiment will be described.

In Step S301, the mobile station MS transmits an upward signalmultiplexed with the quantity of packets accumulated in the transmissionbuffer 213 to the base station BS.

In Step S302, in accordance with reception power of packets in apreceding step period, which is stored in the reception power storagecircuit 119, and the quantity of packets accumulated in the transmissionbuffer 213 of the mobile station MS, which is transmitted from thesignal separation circuit 116, the base station BS calculates radioresources (code resources, slot resources and the like) of the mobilestation MS in a next step period.

In Step S303, the base station BS transmits the calculated radioresources of the mobile station MS in the next step period to the mobilestation MS, by multiplexing the radio resources with a downward signal.

In Step S304, the resource allocation circuit 209 of the mobile stationMS allocates radio resources for packet transmission (in other words,determines transmission power of packets) in the next step period, inaccordance with the radio resources of the mobile station, which arereceived from the base station BS. Thereafter, the packet transmissioncircuit 214 of the mobile station MS transmits an uplink signal to thebase station BS by use of the allocated radio resources.

According to the packet communications system of this embodiment,without having a particularly special configuration, the transmissionpower of packets in the mobile station MS is limited in stages at themobile station MS side. Thus, packet reception failure in another mobilestation can be prevented. In addition, reduction in capacity anddeterioration of QoS satisfaction can be prevented.

Moreover, according to the packet communications system of thisembodiment, influences of interference on burst signals can be reducedand a communication quality can be further improved.

Moreover, according to the packet communications system of thisembodiment, the base station BS can appropriately instruct the mobilestation MS to change the transmission power in the next step period, byuse of the quantity of packets notified from the mobile station MS.

Moreover, according to the packet communications system of thisembodiment, the mobile station MS can perform notification of thequantity of packets together with transmission of packets. Thus, it isnot required to separately notify the quantity of accumulated packets.

Moreover, according to the packet communications system of thisembodiment, the base station BS can periodically allocate the radioresources to be used, by use of the periodically notified quantity ofpackets. Thus, the mobile station can receive allocation of radioresources, which is periodically reviewed, and can be prevented fromreceiving allocation of unnecessary radio resources.

Moreover, according to the packet communications system of thisembodiment, unlike scheduling, it is not required to always exchangeinformation, such as priority and elapsed time, about all transmittedpackets between the mobile stations or between the base station and themobile station, so as to understand the information.

Modified Example 1

Note that the packet communications systems and the packetcommunications methods according to the first to third embodimentsdescribed above can be realized by executing a packet communicationsprogram described in a predetermined computer language on a computerprovided in a base station or a radio control device or on an IC chipincluded in a mobile station such as a portable telephone set.

Specifically, the packet communications program according to thisembodiment is configured to execute each processing described in thefirst to third embodiments described above by use of hardware resourcesincluded in a general purpose computer.

Such a packet communications program is recorded in a recording medium(a floppy disk 116, a CD-ROM 117, a RAM 118 and a cassette tape 119)which can be read by a computer 120 as shown in FIG. 13. Accordingly,the device described in the first to third embodiments described abovecan be realized via this recording medium, through the computer 120 orby directly installing the program in memories of the mobile stationsMS1 to MS3 and the like. Consequently, through these recording media,software can be easily saved in, delivered to or transferred to thecomputer 120.

Moreover, such a packet communications program can be delivered to amobile station used by a user through service modes such as downloadingvia a radio network. Thus, smooth spread of the above-described packetcommunications system and packet communications method can be realized,

Modified Example 2

Moreover, the present invention is not limited to the first to thirdembodiments described above but may have the following various changesadded thereto.

For example, in the above-described embodiments, the packetcommunications system and packet communications method of the presentinvention have been described based on the relationship between the basestation and the mobile station. The present invention can be alsoapplied to a case where a mobile station functions as a relay stationfor another mobile station or a base station, such as an ad hoctechnology and a multi-hop technology, for example.

In this case, when the mobile station as the relay station becomes atransmitting side, the above-described transmission control isperformed. For example, when relaying is performed between anothermobile station and the base station, transmission power control in anuplink for the base station is performed and, at the same time,transmission power control in a downlink for another mobile station isperformed. Moreover, when relaying is performed between base stations,the transmission power control in the uplink for the base stations isperformed.

Moreover, in the first to third embodiments described above, thetransmission power control is performed for the base station or themobile station. However, for example, the transmission power control canbe also performed in a radio control device which controls respectivebase stations.

In this case, interference levels and QoS of respective base stationsare sequentially notified to the radio control device and transmissionpower and an interference level of a mobile station which establishescommunications with the respective base stations are monitored by theradio control device through the respective base stations. Accordingly,a transmission power limit value is calculated by the radio controldevice, and notified to the respective base stations and the mobilestation.

Specifically, a control device for realizing the packet communicationssystem according to the present invention controls transmission power ofpackets in a next step period, in accordance with transmission power ofpackets in a preceding step period and an interference level in areceiving station. Thus, it is needless to say that the control deviceis mounted in a base station and a mobile station. Moreover, the controldevice may be mounted on the radio control device which indirectlycontrols the base station.

Industrial Applicability

As described above, according to the present invention, a transmissionpower limit value in a next step period is determined by use of actualtransmission power of packets in a preceding step period. Thus, anincrease of an interference level in a mobile station belonging toanother cell can be suppressed within a TPC margin. In addition,reduction in capacity and deterioration of QoS satisfaction due toreception failure can be prevented.

In particular, according to the present invention, prediction of thenext step period is performed based on the preceding step period. Thus,influences of interference on burst signals can be reduced and acommunication quality can be further improved.

1. A packet communications system which performs packet communications through a radio link established between a base station and a mobile station and performs a transmission power control for each of a plurality of periods utilized for transmitting packet data therebetween, the system comprising: a transmission power storage which is configured to store transmission power of packets addressed to the mobile station in a second period previous to a first period, each of the first period and the second period being one of the plurality of periods utilized for transmitting packet data; a transmission power limit value calculator configured to calculate a transmission power limit value in the first period, by use of the transmission power stored in the transmission power storage, and a transmission power setter configured to set transmission power of packets addressed to the mobile station in the first period to be smaller than or equal to the transmission power limit value.
 2. A packet communications method for performing packet communications through a radio link established between a base station and a mobile station and for performing a transmission power control for each of a plurality of periods utilized for transmitting packet data therebetween, the method comprising: storing transmission power of packets addressed to the mobile station in a second period previous to a first period, each of the first period and the second period being one of the plurality of periods utilized for transmitting packet data; calculating a transmission power limit value in the first period, by use of the transmission power stored in the transmission power storage; and setting transmission power of packets addressed to the mobile station in the first period to be smaller than or equal to the transmission power limit value.
 3. A base station which performs packet communications through a radio link established between the base station and a mobile station and performs a transmission power control for each of a plurality of periods utilized for transmitting packet data therebetween, the base station comprising: a transmission power storage which is configured to store transmission power of packets addressed to the mobile station in a second period previous to a first period. each of the first period and the second period being one of the plurality of periods utilized for transmitting packet data; a transmission power limit value calculator configured to calculate a transmission power limit value in the first period, by use of the transmission power stored in the transmission power storage, and a transmission power setter configured to set transmission power of packets addressed to the mobile station in the first period to be smaller than or equal to the transmission power limit value.
 4. The base station according to claim 3, further comprising: a quality of service monitor configured to monitor a quality of service in the radio link, and wherein the transmission power setter is configured to set the transmission power in the first period to exceed the transmission power limit value within maximum available transmission power of the base station, when the quality of service is smaller than or equal to a predetermined value.
 5. The base station according to claim 3, wherein the transmission power setter is configured to set the transmission power in the first period, in accordance with an interference level of the base station, when the transmission power of packets in the second period is 0 .
 6. The base station according to claim 3, wherein the transmission power setter sets the transmission power in the first period based on an average value of interference level received by the transmitting station in a fixed period previous to the first period.
 7. The base station according to claim 3, wherein the transmission power setter is configured to set the transmission power of packets in the first period, in accordance with an average value of transmission power of packets in a fixed period previous to the first period, when the transmission power of packets in the second period is 0 .
 8. A computer readable medium including computer program instructions which cause a computer to implement a method for performing packet communications through a radio link established between a transmitting station and a receiving station and for performing a transmission power control for each of a plurality of periods utilized for transmitting packet data therebetween: storing transmission power of packets addressed to a mobile station in a second period previous to a first period. each of the first period and the second period being one of the plurality of periods utilized for transmitting packet data; and calculating a transmission power limit value in the first step period, by use of the transmission power stored in the transmission power storage, setting transmission power of packets addressed to the mobile station in the first period to be smaller than or equal to the transmission power limit value. 